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Phase 1b - Neurology & Neuroscience > Visual System - Anatomy > Flashcards

Visual System - Anatomy Flashcards

1
Q

Which anatomical space does the eye reside within?

A
  • Orbit
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2
Q

Name structure 1.

A

Upper eyelid

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3
Q

Name structure 2.

A

Palpebral fissure

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4
Q

Name structure 3.

A

Lateral canthus

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5
Q

Name structure 4.

A

Lower eyelid

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6
Q

Name structure 5.

A

Pupil

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7
Q

Name structure 6.

A

Iris

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8
Q

Name structure 7.

A

Sclera

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9
Q

Name structure 8.

A

Medial canthus

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10
Q

Name structure 9.

A

Caruncle

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11
Q

Name structure 10.

A

Limbus (border between cornea and sclera)

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12
Q

What is the space between the lateral and medial canthus of the eye?

A
  • Palpebral fissure
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13
Q

What term refers to the lateral confluence of the upper and lower eyelid regions?

A
  • Lateral canthus
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14
Q

What term refers to the medial confluence of the upper and lower eyelid regions?

A
  • Medial canthus
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15
Q

What is the opening within the iris?

A
  • Pupil
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16
Q

Which globular nodule structure resides besides the medial canthus of the eye?

A
  • Caruncle
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17
Q

Which structure is the border between the cornea and sclera?

A
  • Limbus
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18
Q

Where is the lacrimal gland located?

A
  • Located within the orbit, latero-superior to the globe
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19
Q

What is the function performed by the lacrimal gland?

A
  • It continually releases fluid (tears) which cleanses & protects the eye’s surface as it lubricates and moistens it
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20
Q

How are tears drained by the lacrimal system (5 steps)?

A
  1. Tears produced by lacrimal gland
  2. Drain through the two puncta, opening on medial lid margin
  3. Flow through superior & inferior canaliculi
  4. Gather in tear sac
  5. Exit tear sac through tear duct into nasal activity
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21
Q

Which two superior and inferior eyelid structures are responsible for tear film drainage?

A

2 Puncta: Superior and inferior canaliculi

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22
Q

How are tears drained from the puncta to the tear sac?

A
  • Tears flow through the superior and inferior canaliculi to the tear sac
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23
Q

What is the fate of tears within the tear sac?

A
  • Exit the tear sac through the tear duct into the nasal cavity
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24
Q

What are the three types of tears?

A
  • Basal
  • Reflex
  • Emotional (crying)
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25
Q

What are the functions of the basal tears (3)?

A
  • Basal tears are your basic functional tear:
    • Released continuously in tiny quantities to lubricate the cornea and keep it clear of dust
    • Vital to ensure good visual acuity and comfort
    • Basal tears also fight against bacterial infection as a part of the immune system
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26
Q

Which tears are referred to the increased tear production in response to ocular irritation?

A
  • Reflex tear
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27
Q

What does the tear pathway comprise of?

A

Afferent pathway → CNS → Efferent pathway → Lacrimal gland

Neurotransmitter: acetylcholine

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28
Q

Which afferent nerve innervates the cornea?

A
  • Sensory nerve fibres via the ophthalmic branch of trigeminal nerve
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29
Q

How is the efferent pathway mediated?

A
  • Mediated by the parasympathetic nerve, innervating the lacrimal gland
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30
Q

What is the function of the tear film?

A
  • Maintains smooth cornea-air surface
  • Oxygen supply to Cornea – normal cornea has no blood vessels
  • Removal of debris (tear film and blinking)
  • Bactericide
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31
Q

How many layers comprise the tear film? Name them.

A

Three:

  • Superficial Lipid Layer (to reduce tear film evaporation - produced by a row of Meibomian Glands along the lid margins)
  • Aqueous Tear Film
  • Mucinous Layer Corneal Surface (maintains surface wetting)
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32
Q

Which glands along the lid margins produce the superficial lipid layer of the tear film?

A
  • Meibomian glands
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33
Q

What is the function of the lipid layer of the tear film?

A
  • Responsible for protecting the tear film from rapid evaporation
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34
Q

What is the purpose of the mucinous layer corneal surface?

A
  • Maintains surface wetting
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35
Q

Which tear film layer forms the main bulk of the tear film?

A
  • The water layer
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36
Q

How do mucin molecules regulate surface wetting of the corneal epithelial surface?

A
  • The mucin molecules act by binding water molecules to the hydrophobic corneal epithelial cell surface
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37
Q

Which thin transparent tissue covers the outer surface of the eye?

A
  • Conjunctiva
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38
Q

Describe the anatomical course of the conjunctiva.

A
  • Origin: Outer edge of the cornea
  • Anatomical relations: Covers visible part of the eye & Lines the inside of the eyelids
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39
Q

What function is performed by the conjuctiva (3)?

A
  • The conjunctiva of the eye provides protection and lubrication of the eye by the production of mucus and tears
  • Prevents microbial entrance into the eye and plays a role in immune surveillance
  • It lines the inside of the eyelids and provides a covering to the sclera
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40
Q

How is conjunctiva nourished with nutrients and oxygen?

A
  • Tiny blood vessels
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41
Q

What is the average antero-posterior diameter of the eye?

A
  • 24mm in adults
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42
Q

What are the 3 layers of the eye?

A
  • Sclera
  • Choroid
  • Retina
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43
Q

What is the function of the sclera?

A
  • The outer fibrous opaque layer responsible for protecting the eye and maintaining shape (high water content)
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44
Q

Describe the water content of the sclera:

A
  • High water content
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45
Q

How many layers form the cornea? Name them.

A
  • Epithelium
  • Bowman’s membrane
  • Stroma (its regularity contributes towards transparency)
  • Descemet’s membrane
  • Endothelium (pumps fluid out of the cornea and prevent corneal oedema)
46
Q

The regularity of which corneal layer contributes towards transparency?

47
Q

Which corneal structure pumps fluid out of the cornea and prevents corneal oedema?

A
  • Endothelium
48
Q

Describe the water content of the cornea:

A
  • Low water content
49
Q

What property of the cornea provides 2/3 of the eye’s focussing power?

A
  • Refractive index
50
Q

What provides oxygen supply to the anterior segment of the eye (cornea)?

A
  • The tear film considering there are no blood vessels supplying the cornea
51
Q

What is the uvea?

A
  • The most vascular coat of the eyeball and lies between the sclera & retina
52
Q

Where does the uvea reside?

A
  • Between the sclera and retina
53
Q

What three structures comprise the uvea?

A
  • Iris
  • Ciliary body
  • Choroid
54
Q

Which eye layer is pigmented and vascular?

55
Q

Where does the choroid lie?

A

Between the retina and sclera

56
Q

What is the function of the choroid?

A
  • Responsible for providing circulation to the eye & shielding out unwanted scattered light
57
Q

What is the iris?

A

Round opening in the centre is the pupil

58
Q

What is the function of the iris?

A

Controls light levels inside the eye similar to the aperture on a camera

59
Q

What is the outer capsule of the lens?

A
  • Outer acellular capsule
60
Q

Which fibres comprise the core of the lens?

A
  • Regular inner elongated cell fibres - providing transparency
61
Q

What are the 4 main functions of the lens?

A
  • Provide transparency
  • Regular structure
  • Refractive power, 1/3 of the eye focussing power (higher refractive index than aqueous fluid and vitreous)
  • Elasticity & accommodation
62
Q

What is the innermost neurosensory layer of the eye?

63
Q

Which nerve transmits electrical impulses to the visual processing centres of the brain?

A
  • Optic nerve
64
Q

What term describes the visual portion of the optic nerve?

A
  • Optic disc
65
Q

Where is the optic blind spot located?

A
  • Where the optic nerve meets the retina, there are no light sensitive cells (Rods and Cones)
66
Q

Where is the macula located?

A
  • Centre of the retina, temporal to the optic nerve
67
Q

What is the macula?

A
  • A small and highly sensitive part of the retina responsible for detailed central vision
68
Q

What is the fovea?

A
  • A small depression in the retina of the eye where visual acuity is highest
    • ​The centre of the field of vision is focused in this region, where retinal cones are particularly concentrated
69
Q

Which structure is located at the very centre of the macula?

70
Q

Which structure is the most sensitive part of the retina?

71
Q

Which photoreceptor cells are found at their highest concentration within the fovea?

A
  • Cone cells to perceive in detail
72
Q

What is the corresponding landmark for the physiological blind spot?

A
  • The optic disc
73
Q

What is central vision?

A
  • Central / Foveal / Macular vision is responsible for detailed central fine vision and daytime colour vision
    • Reading, fascial recognition
74
Q

How is central vision assessed?

A
  • Visual acuity assessment
75
Q

What is associated with a loss of foveal vision?

A
  • Poor visual acuity
76
Q

What is peripheral vision?

A
  • Specialises in detecting shape & movement in the environment
    • Night vision, navigation vision
77
Q

What is associated with a loss of central vision?

A
  • Problems with reading and recognising faces
78
Q

How is peripheral vision assessed?

A
  • Visual field assessment
79
Q

An extensive loss of peripheral vision is associated with what?

A
  • Inability to navigate within the environment
    • Needs white stick despite perfect visual acuity
80
Q

What is the neuroretina?

A
  • The inner thicker layer comprising of retinal ganglion cells, and photoreceptors
81
Q

How many layers form the neuroretina?

A

Three:

  • Outer photoreceptor
  • Middle bipolar
  • Inner retinal ganglion cells
82
Q

Which cells comprise the outer layer of the retina? What is their funciton?

A
  • Photoreceptors (1st order neurones)

Detection of light

83
Q

Which cells comprise the middle layer of the retina? What is their function?

A
  • Bipolar cells (2nd order neurones)

Local signal processing to improve contrast sensitivity, regulate sensitivity

84
Q

Which cells comprise the inner retinal layer?

A
  • Retinal ganglion cells (3rd order neurone)

Transmission of signal from the eye to the brain

85
Q

What is the function performed by the retinal pigment epithelium?

A
  • Transports nutrient from the choroid to the photoreceptor cells, and removes metabolic waste from the retina
86
Q

What are the two main classes of photoreceptor cells?

A
  • Rod & cone cells
87
Q

What are the characteristics of rod photoreceptor cells (4)?

A
  • 100 times more sensitive to light than cones
  • Slow response to light
  • Scotopic vision
  • 120 million rods
88
Q

What are the characteristics of cone photoreceptor cells (4)?

A
  • Less sensitive to light
  • Faster response to light
  • Responsible for day light fine vision & colour vision (photopic vision)
  • 6 million cones
89
Q

Which photoreceptor cells are concerned with peripheral and night vision?

A
  • Rod cells

More photoreceptors, more pigment, higher spatial and temporal (time) summation
Recognizes motion

90
Q

Which photoreceptor cells are concerned with central and day vision?

A
  • Cone cells

Recognizes colour and detail

91
Q

Where are the mitochondria located within the photoreceptors?

A
  • Inner segments
92
Q

What are the outer segments comprised of?

A
  • Discs, that contain rhodopsin
93
Q

Which pigment resides within the outer segment of rod cells?

94
Q

What are the 2 components of rhodopsin?

A
  • Opsin and Retinal
95
Q

Upon exposure to photons of light, rhodopsin exists in which form?

A
  • From cis-form to trans-form upon exposure to photons of light
96
Q

What happens to rhodopsin upon light exposure?

A
  • Bleaching: Photon interactions result in isomerisation of retinal from the cis to trans-form, subsequently degenerating the rhodopsin molecule into it’s constituent components, opsin and trans-retinal
97
Q

What is the fate of deactivated photo-pigments in the outer segment (3 steps)?

A
  1. Phagocytossed by the retinal epithelial cells
  2. Regenerated inside the retinal epithelial cells
  3. Transported back to the photo-receptors
98
Q

Describe the density and distribution of rod photoreceptors:

A
  • Widely distributed throughout the retina
    • Highest density outside the macula (absent within the macula), progressively decreasing towards the periphery
99
Q

Where are cone photoreceptors located?

A
  • Distributed exclusively within the macula
100
Q

Where can one find the highest concentration of rod photoreceptors in the retina?

A

20-40 degrees away from the fovea

101
Q

What are the 3 types of cone cells?

A
  • S-cones
  • M-cones
  • L-cones
102
Q

What is the peak light sensitivity of rod cells?

103
Q

Which cone cells are sensitives to short wavelengths (blue)?

104
Q

Which cone cells are sensitive to medium wavelengths (green)?

105
Q

Which colour are L-cones sensitive too?

A

Red colour

106
Q

Which cone cells are stimulated by yellow light?

A

M- and L-cones equally

Combination of green and red light

107
Q

What is the commonest form of colour vision deficiency?

A

Deuteranomaly (Daltonism)

108
Q

What is deuteranomaly?

A

Cannot perceive the colour red

Caused by the shifting of the M-cone sensitivity peak towards that of the L-cone curve, causing red-green confusion

109
Q

What is full colour blindness called?

A

Achromatopsia

110
Q

What test is conducted to detect colour blindness?

A

Ishihara test

Phase 1b - Neurology & Neuroscience (18 decks)

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